For me it has always been obvious. I think the people who do not believe in God are not too bright to be honest.
I first acknowledged God through a Christmas play we had, and a lutheran pastor was visiting and started the event with praying and saying "Heavenly Father" and that is when I decided in my small head to also talk to that guy! I believe nothing comes out of nothing. That there is a God is self-evident, but then one can ask which god?
I think proving the God of the bible to be the correct one is fairly easy. All the other "holy" books other religions have are just bad poetry and incoherent babblings. The bible is the only consistent work written by many different authors during thousands of years and yet is consistent.
Add to this the historical accuracy, the impossible prophecies that have been fulfilled and the preservation of Israelites and you got a compelling case.
Show me where are the hittites, the amalakites, the philistines? No where, but there are still Hebrews.
Hebrew is the oldest known language still alive today.
One final proof is that God is personal, God is close. So the personal testimony angle cannot be overlooked as proof in my opinion.